JP2811360B2 - Information recording medium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an information recording medium on or from which information can be recorded or reproduced by a laser.

[Technical Background of the Invention] In recent years, information recording media using a beam of high energy density such as laser light have been developed and put into practical use. This information recording medium is generally called an optical disk,
It can be used as a video disk, an audio disk, as well as a large capacity still image file and a large capacity computer disk memory. Furthermore, optical cards, optical tapes, and the like are also known as information recording media.

Video discs, audio discs (compact discs (CDs)), etc. have already been put into practical use as read-only optical discs, and can be written in DRAW.
(Direct Read After Write) type optical disks and erasable type optical disks capable of rewriting information are also being developed, and some of them have been put to practical use.

Such a DRAW type information recording medium has, as a basic structure,
A disc-shaped transparent substrate made of plastic, glass, etc.,
It has a recording layer made of a metal or semimetal such as Bi, Sn, In, Te or the like, or a dye provided thereon. Recording (writing) of information on the optical disk is performed, for example, by irradiating a laser beam to the optical disk.

In general, laser irradiation is performed by focusing the laser on the recording layer or signal formation surface through a substrate made of a transparent material to mitigate the occurrence of reading errors due to dust during recording or reproduction. Done. This is performed similarly in the case of a recording optical disk and the case of a reproduction optical disk. However, by irradiating the laser from the substrate side in this way, it is hardly affected by dust or the like at the time of recording or reproduction, but there is a problem that a loss of light amount occurs due to the reflection of the laser on the substrate surface.

For this reason, in an information recording medium having a recording function, a large laser power is required at the time of recording, and the amount of a reflected signal becomes small at the time of reproduction. Therefore, there is a problem that a tracking error or a reading error occurs. Alternatively, when the difference in the refractive index between the substrate and the recording layer is small, there is a problem that focusing is easily performed not on the recording layer but on the substrate.

In order to solve such a problem, the provision of the anti-reflection layer made of a material MgF ₂ or the like on the surface of the substrate (JP 60-89
844) and providing an anti-reflection layer made of a material such as MgF ₂ , 3NaF / AlF ₃ (see Japanese Patent Application Laid-Open No. 60-138749).

The anti-reflection layer as described above is effective in preventing the occurrence of the tracking error and the reading error since the reflectance on the substrate surface is reduced, but since the material of the anti-reflection layer is an inorganic compound, In order to form the prevention layer, it is necessary to perform vacuum deposition such as vacuum deposition and sputtering. Such an inorganic compound vapor-deposited film has a problem that its adhesion to a process substrate is not sufficient, or it is easily deteriorated when stored for a long period of time, and its surface is easily damaged, and its durability is not sufficient. Further, the layer formation method by vapor deposition as described above has disadvantages in manufacturing such as an increase in cost and a complicated process.

The present inventors are effective as an antireflection layer when a layer made of polysiloxane is provided on the surface of a substrate, and a layer made of polysiloxane is applied with a solution containing siloxane,
It has been found that it can be easily formed by drying, but it has been difficult to form a layer composed of polysiloxane on the surface of a polycarbonate substrate with high adhesion.
However, the problem of adhesion was solved by interposing an undercoat layer between the substrate and the anti-reflection layer made of polysiloxane, and the present invention was completed.

[Object of the Invention] An object of the present invention is to provide a novel information recording medium having an antireflection layer which can be easily formed by a coating method.

In addition, the present invention provides a novel information recording method in which an antireflection layer having excellent adhesion to a polycarbonate substrate is provided, which has a high reflectance and does not cause a reproduction error such as a tracking error when reproducing a recording signal. The purpose is to provide a medium.

Furthermore, in addition to preventing the reflectance from lowering, the present invention has an excellent adhesion to a polycarbonate substrate, can reduce surface scratches, has an excellent antistatic property, and has a function of protecting an optical disk such that dust is unlikely to adhere. It is another object of the present invention to provide an information recording medium having an excellent high-strength anti-reflection layer.

[Summary of the Invention] The present invention relates to a method of manufacturing a polycarbonate substrate on one surface.
A recording layer capable of recording or reproducing information by a laser is provided, and the surface of the substrate on which the recording layer is not provided is made of polysiloxane via an undercoat layer, and
An information recording medium provided with an antireflection layer having a thickness of 0 °.

 Preferred embodiments of the present invention are as follows.

1) The information recording medium as described above, wherein the undercoat layer is made of polymethyl methacrylate, ethyl acrylate / methacrylic acid ester copolymer, or N-methylol acrylamide.

2) The information recording medium, wherein the recording layer is a layer made of a dye.

3) The information recording medium as described above, wherein a reflective layer is laminated on the recording layer.

4) The information recording medium, wherein a reflective layer and a protective layer are laminated on the recording layer in this order.

[Effects of the Invention] The information recording medium of the present invention is, as described above, a specific material provided on the surface of the substrate on the laser light incident side, which is the surface opposite to the surface having the recording layer. And has an antireflection layer having a thickness in a specific range.

The anti-reflection layer in the information recording medium of the present invention has a function of preventing reflection of light on the substrate surface and preventing a decrease in reflectance on the recording layer surface, similarly to an optical disk having a conventional anti-reflection layer. . Accordingly, information can be recorded with a low laser power, and the gain of a servo signal for tracking or the like or a reproduction signal such as an information signal can be increased. As a result, when reproducing the recording signal, the occurrence of a reproduction error such as a tracking error can be significantly reduced.

Further, the antireflection layer in the information recording medium of the present invention,
It also has antistatic performance, and has a large adhesive force with the substrate, so that dust does not easily adhere to the surface of the information recording medium on the laser beam incident side and has excellent scratch resistance.

[Detailed Description of the Invention] The information recording medium of the present invention is provided with a recording layer on one surface of a polycarbonate substrate, and an undercoat layer on a surface of the substrate on which the recording layer is not provided. It has a basic structure provided with an antireflection layer.

The substrate in the present invention is a substrate manufactured from polycarbonate.

An intermediate layer may be provided on the surface of the substrate on which the recording layer is provided, for the purpose of improving flatness, improving adhesive strength, improving the solvent resistance of the substrate, and preventing deterioration of the recording layer. Examples of the material of the intermediate layer include polymethyl methacrylate, acrylic acid ester / methacrylic acid ester copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, and styrene.
Sulfonic acid copolymer, styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer,
Polymeric substances such as ethylene / vinyl acetate copolymer, polyethylene a, polypropylene, polycarbonate, epoxy resin; organic substances such as silane coupling agents and titanate coupling agents; and inorganic dielectrics (SiO ₂ , Zn
Inorganic substances such as S, AlN, Si ₃ N ₄ ) and inorganic fluoride (MgF ₂ ).

The intermediate layer is formed, for example, by dissolving or dispersing the above substance in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. can do. The thickness of the intermediate layer is generally in the range from 0.005 to 20 μm, preferably in the range from 0.01 to 10 μm.

Surface of the above substrate on which the recording layer is formed (or the surface of the intermediate layer)
In order to perform good tracking during recording or reproduction, pre-grooves (tracking grooves) and pre-pits indicating information such as address signals are formed.

The pregrooves and prepits may be provided directly on the substrate surface by injection molding or extrusion molding. Further, a pre-groove layer and a pre-pit layer for forming the pre-groove and the pre-pit may be provided on the surface of the substrate.

As a material for the pregroove layer or the like, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used.

The pre-groove layer and the like are formed by first applying a mixed solution comprising the above-mentioned acrylate ester and a polymerization initiator on a precisely formed master (stamper), and then placing a substrate on the coating solution layer. Then, the liquid-liquid layer is cured by irradiating ultraviolet rays through the substrate or the matrix to fix the substrate and the liquid phase. Next, the substrate provided with a pre-groove layer or the like is obtained by peeling the substrate from the matrix. The thickness of the pregroove layer is generally in the range of 0.1 to 100 μm, preferably in the range of 0.1 to 50 μm.

On a substrate (or a pre-groove layer or the like) on which pre-grooves and pre-pits are formed, using a material similar to the material for forming the intermediate layer, to protect from a solvent in a coating solution for forming a recording layer. May be provided.

A recording layer containing a dye is provided on one surface of the substrate. By irradiating laser light from the substrate side to form pits for reproduction in the recording layer, information is recorded on the recording layer.

The dye used in the present invention is not particularly limited, and any dye may be used. For example, cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes,
Pyrylium dyes, thiopyrylium dyes, azulenium dyes, squarylium dyes, metal complex salt dyes such as Ni and Cr, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, indoaniline dyes,
Triphenylmethane dye, triallylmethane dye,
Dyes such as aluminum dyes, diimmonium dyes, nitroso dyes, leuco dyes, cronconium dyes, and the like can be given.

These dyes are not limited to the light once (WO) type,
It may be of a rewritable (RW) type (or reversible type).

Among these dyes, a dye having a high absorptivity to light in the near red region of 700 to 900 nm is preferable because a semiconductor laser that emits near-infrared light is practically used as a recording / reproducing laser.

In particular, cyanine dyes, azulenium dyes, and squarylium dyes are preferable, and among the cyanine dyes, naphthoindolenine dyes and imidazoquinoxaline dyes are preferable.

These may be used alone or as a mixture of two or more. When a cyanine dye is used, the metal complex salt dye, the aminium dye, or the diimmonium dye is preferably used together as a quencher. In this case, it is preferable that a metal complex salt dye or the like is contained as a quencher at a ratio of 0.001 to 0.3 mol based on 1 mol of all dyes.

Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene; aliphatic hydrocarbon solvents such as hexane, octane, nonane, and cyclohexane; and organic acid solvents such as acetic acid. Ester solvents such as ethyl acetate, butyl acetate, amyl acetate, ethylene glycol monoethyl ether acetate, cellosolve acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone;
Halogenated hydrocarbon solvents such as 1,2-dichloroethane, chloroform, methyl chloroform, trichlene, carbon tetrachloride, tetrachloroethylene; ether solvents such as tetrahydrofuran, ethyl ether, isopropyl ether, dioxane, diglyme; ethanol; n-propanol, isopropanol, n-
Alcohol solvents such as butanol, amyl alcohol, diacetone alcohol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and benzyl alcohol; amide solvents such as dimethylformamide; 2, 2, 3, 3 Fluorinated alcohols such as tetrafluoropropanol, fluorinated ketones, fluorinated esters, fluorinated amides, fluorinated ethers, fluorinated aromatic hydrocarbons, fluorinated solvents such as fluorinated aliphatic hydrocarbons, etc. Can be mentioned.

The recording layer prepares a dye solution from the dye and the solvent as described above, and for example, this dye solution is spray-coated, spin-coated, dipped, roll-coated, blade-coated, doctor-rolled, and screen-printed. Etc., and can be formed by drying. In particular, it is preferable to form by a spin coating method, in which case, the concentration of the dye in the dye solution is 0.5
It is preferably from 15 to 15% by weight, especially from 1 to 10% by weight, more preferably from 1.5 to 8% by weight.

The dye solution further contains an antioxidant, a UV absorber,
Various additives such as a plasticizer and a lubricant may be added according to the purpose.

When a binder is used, examples of the binder include cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate; natural organic polymer substances such as dextran, rosin, and rubber; and carbonized materials such as polyethylene, polypropylene, polystyrene, and polyisobutylene. Hydrogen resins, polyvinyl chloride, polyvinylidene chloride, vinyl resins such as polyvinyl chloride / polyvinyl acetate copolymer, acrylic resins such as polymethyl acrylate and polymethyl methacrylate,
Synthetic organic polymer substances such as polyvinyl alcohol, chlorinated polyolefin, epoxy resin, butyral resin, rubber derivatives, and initial condensates of thermosetting resins such as phenol / formaldehyde resins can be given.

When applying the above-mentioned dye solution on a substrate by a spin coating method, it can be performed using a device and a method known per se. The above dye solution is generally used in an amount of 0 to 100.
C., preferably 5 to 80.degree. C., more preferably 10 to 60.degree. The number of rotations of the substrate is generally 10 to 1000 rpm when the dye solution is applied, preferably 100 to 500 rpm.When the dye coating is dried, it is generally 300 to 10000 rpm, particularly 500-7000r.pm, especially 7
It is preferably set to 00 to 40000 rpm.

An undercoat layer is provided on the surface of the substrate on which the recording layer is not provided in the information recording medium of the present invention.

Examples of the material of the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N
-Methylol acrylamide, styrene / sulfonic acid copolymer, styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide,
Polymer substances such as vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, epoxy resin; and organic substances such as silane coupling agent and titanate coupling agent. . Particularly, polymethyl methacrylate, acrylate / methacrylate copolymer, N-methylol acrylamide and the like are preferable.

The undercoat layer preferably has a thickness of 0.01 to 0.5 μm. This undercoat layer can be formed by the same method as in the case of the intermediate layer that may be provided between the substrate and the recording layer.

If an antireflection layer made of polysiloxane is formed directly on the surface of a polycarbonate substrate without providing an undercoat layer, the adhesion between the substrate and the antireflection layer is small, and the antireflection layer is easily peeled off.

On this undercoat layer, consisting of polysiloxane, 600-4
An antireflection layer having a thickness of 000, preferably 1000 to 30,000 is provided.

This antireflection layer is formed by applying a liquid material (colloidal dispersion, suspension, solution, etc.) containing a siloxane-based compound to the surface of the substrate by the same method as described for the application of the dye solution. Then, the coating can be carried out by drying the coating at room temperature or at an elevated temperature. During the drying of the coating film, the siloxane compound condenses to form an antireflection layer mainly composed of polysiloxane having a network structure. This antireflection layer adheres strongly to the surface of the substrate due to the anchoring effect when the substrate is plastic. The refractive index of the antireflection layer is about 1.30 to 1.45. Examples of the liquid material containing a siloxane-based compound include a siloxane-based antistatic agent [Colcoat (registered trademark)] sold by Taiyo Bussan Co., Ltd.

In the information recording medium of the present invention, it is necessary that the thickness of the antireflection layer is in the range of 600 to 40,000 °. The preferred thickness of the anti-reflection layer is in the range of 1000 to 3000 °. When the thickness of the anti-reflection layer is smaller than the above range, the reflectance of the information recording medium is low, and is substantially the same as the reflectance without providing the anti-reflection layer at all. Lower.

When forming the antireflection layer on the undercoat layer, the antireflection layer forming material may be applied after the undercoat layer is completely dried, but the solvent before the undercoat layer is completely dried may be slightly When an antireflection layer-forming material is applied on the remaining undercoat layer, the adhesion of the antireflection layer may be further increased.

Note that the anti-reflection layer may be formed on a substrate on which a recording layer is not provided after forming a recording layer on a substrate, if desired, a reflection layer, a protective layer, or the like. Before providing, it may be provided first on the side of the substrate where the recording layer is not provided.

A reflective layer may be further provided on the recording layer of the information recording medium of the present invention.

As the material of the reflection layer, Be, B, C, Sc, Rb, Sr, A
s, Os, Tl, At, Fr, Ra, Mg, Se, Y, Ti, Zr, Hf,
V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, R
h, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, S
Metals and metalloids such as i, Ge, Te, Pb, Po, Sn, Bi, and Sb can be mentioned. Among them, C, Au, Zn, C
u, Pt, Al, Ni, In and stainless steel are particularly preferred.
These substances may be used alone or in combination of two or more kinds or as an alloy.

The reflection layer can be formed on the recording layer by, for example, vapor deposition, sputtering, or ion plating of the above-mentioned light reflective substance. In particular, it is preferable to form the reflective layer by sputtering. The thickness of the reflective layer is generally in the range from 100 to 3000, preferably from 400 to 2000.

When a noble metal reflective layer is provided as a reflective layer,
A metal adhesion layer such as Al or an organic adhesion layer can be provided.

On this reflective layer, a protective layer may be provided for the purpose of physically and chemically protecting the entire information recording medium, particularly the recording layer and the reflective layer.

Examples of the material used for the protective layer include inorganic substances such as SiO, SiO ₂ , Si ₃ N ₄ , MgF ₂ , and SnO ₂ . Further, examples of the organic substance include a thermoplastic resin, a thermosetting resin, a UV-curable resin, and the like, and a UV-curable resin is preferable.

The protective layer can be formed by, for example, dissolving a thermoplastic resin, a thermosetting resin, or the like in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. In the case of a UV-curable resin, a protective layer can be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying the coating solution, and irradiating with UV light to cure. UV curable resins include oligomers of (meth) acrylates such as urethane (meth) acrylate, epoxy (meth) acrylate and polyester (meth) acrylate, monomers such as (meth) acrylate, and photopolymerization initiator Ordinary UV-curable resins such as can be used. Various additives such as an antistatic agent, an antioxidant and a UV absorber may be added to these coating solutions according to the purpose. It is preferable to use a UV curable resin as a material for the protective layer.

The thickness of the protective layer is generally 0.1 to 100 μm, preferably 0.1 to 100 μm.
It is in the range of 5-20 μm.

In addition to the above, the protective layer can be formed, for example, by laminating a film obtained by extrusion of a plastic onto the dye recording layer via an adhesive layer. Alternatively, it may be provided by a method such as vacuum deposition, sputtering, or coating.

The information is recorded on the information recording medium of the present invention from the substrate side while rotating the information recording medium at a constant linear speed (preferably 1.2 to 2.8 m / sec, particularly preferably 1.2 to 1.4 m / sec). This is performed by irradiating a laser beam to the bottom of the pre-groove to form a bit for reproduction on a recording layer on the groove and record a signal. It is preferable to record an EFM signal in a CD format as a signal in order to obtain the effects of the present invention.
Generally, a semiconductor laser beam having an oscillation wavelength in the range of 750 to 850 nm is used as the recording light. With the information recording medium of the present invention, recording can be performed with a laser power of 10 mW or less.

The bits after the above-described recording are such that the substrate and / or the dye generate heat when irradiated with a laser beam, and melt, evaporate, sublime, deform or change in quality, thereby forming a convex, wavy, or
This is a form in which a change such as a concave shape occurs, a change occurs in a dye, or a change occurs between a dye and a metal reflective layer.

By the above recording method, by recording a CD format signal and the like at a constant linear speed on the information recording medium of the present invention,
Excellent recording / reproducing characteristics such as signal modulation and reproduction C / N can be obtained. Also, since the optical disc of the present invention has a high reflectance, the recorded CD format signal can be
It can be played using a player.

Hereinafter, Examples and Comparative Examples of the present invention will be described. However, these examples do not limit the present invention.

[Example 1] A disc-shaped polycarbonate substrate provided with a pre-groove on almost the entire surface (outer diameter: 120 mm, inner diameter: 15 mm, thickness: 1.2 m)
m, track pitch: 1.6 μm, half width of groove: 0.55 μ
m, groove depth: 90 nm).

On the other hand, the following structural formula Was dissolved in 2,2,3,3-tetrafluoro-1-propanol to prepare a dye solution containing 1.7% by weight of the dye.

This dye solution was maintained at 24 ° C., and the dye solution was spin-coated on one surface of the substrate by a spin coating method at a substrate rotation speed of 20 °.
After applying for 3 seconds at a speed of 0 rpm, the rotation speed is 1000 rpm.
For 5 seconds to form a recording layer.

Under the conditions of 480 W, target-substrate distance 95 mm, gas pressure 2 Pa, and rate 2 nm / sec, Au was DC
By sputtering, a reflective layer made of Au having a thickness of 1000 ° was formed.

A UV curable resin (trade name: 3070, manufactured by Three Bond Co.) is applied as a protective layer on the reflective layer by a spin coating method at a rotation speed of 1500 rpm, and then cured by irradiating ultraviolet rays with a high-pressure mercury lamp. Then, a protective layer having a thickness of 2 μm was formed.

Next, an alcohol / glycolethyl solution containing 4% by weight of polymethyl methacrylate is applied to the surface of the substrate on which the recording layer is not provided by spin coating,
The coating was dried at about 24 ° C. to form an undercoat layer having a thickness of 0.1 to 0.2 μm.

Next, a siloxane-based antistatic agent (available from Taiyo Bussan Co., Ltd., trade name “Colcoat N-103X”) is applied by spin coating on the undercoating layer in which a slight solvent odor remains.
The coating was dried at room temperature (about 24 ° C.) for about 30 minutes to form an antireflection layer having a thickness of 2000 mm.

The thickness of the antireflection layer was measured by a destructive inspection method in which a cut surface was observed with an SEM.

Thus, an information recording medium having a dye recording layer, a reflective layer and a protective layer provided on one side of the substrate and an antireflection layer provided on the reflective side of the substrate was manufactured.

For this information recording medium, by the following evaluation method,
The groove reflectivity and adhesion were measured. First evaluation result
It is described in the table.

[Evaluation of information recording medium] 1) Groove reflectivity (%) Irradiation is performed on a groove in an unrecorded portion with a laser. I asked.

2) Adhesion strength The anti-reflection layer is formed with 100 knives on the surface with a knife, and cellotape (manufactured by Nichiban Co., Ltd.) is adhered to the surface. Peeled off. The adhesive strength is indicated by the number of the bases peeled off by the cellophane tape in the antireflection layer of the bases.

Comparative Example 1 An information recording medium was manufactured in the same manner as in Example 1 except that the antireflection layer and the undercoat layer were not provided.

This information recording medium was evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 An information recording medium was manufactured in the same manner as in Example 1 except that the thickness of the antireflection layer was changed to 500 °.

This information recording medium was evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 An information recording medium was manufactured in the same manner as in Example 1 except that the undercoat layer was not provided.

This information recording medium was evaluated in the same manner as in Example 1. Table 1 shows the results.

As is clear from the results in Table 1, the information recording medium of the present invention obtained in Examples has a high groove reflectivity and a sufficiently high adhesion of the antireflection layer. On the other hand, the information recording medium having no antireflection layer obtained in Comparative Example 1 has a low groove reflectivity and has an antireflection layer having a small thickness outside the range of the present invention obtained in Comparative Example 2. The information recording medium had a groove reflectivity as low as that of the information recording medium obtained in Comparative Example 1, and the antireflection layer did not fulfill its function. In the information recording medium without the undercoat layer obtained in Comparative Example 3, the antireflection layer was completely peeled off in the evaluation of the adhesion, and the adhesion of the antireflection layer was extremely low.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/24 538

Claims (1)

(57) [Claims] 1. One surface of a polycarbonate substrate,
A recording layer capable of recording or reproducing information by a laser is provided, and the surface of the substrate on which the recording layer is not provided is made of polysiloxane via an undercoat layer, and
An information recording medium comprising an antireflection layer having a thickness of 0 °.